Sealed beam high intensity xenon lamp with cooling structure

ABSTRACT

A short arc high intensity xenon lamp is enclosed within a sealed housing made of a light transmissive lens and a parabolic reflector shell. The parabolic shell has a plurality of external air ducts through which air is forced to cool the heated lamp. The air cooled metallic reflector shell permits an increase in efficiency, light intensity and life of the lamp.

United States Patent Beese SEALED BEAM HIGH INTENSITY XENON LAMP WITH COOLING STRUCTURE [72] Inventor: Norman C. Beese, Verona, NJ.

[73] Assignee: International Telephone and Telegraph Corporation, Nutley, NJ.

[22] Filed: Sept. 25, 1970 [21] Appl. No.: 75,590

[52] US. Cl. ..313/24, 313/25, 313/44, 313/113, 313/184 [51] Int. Cl ..II0lj 61/52 [58] Field of Search ..313/25, 24, 20, 33, 44, 113, 313/184; 240/47 [56] References Cited UNITED STATES PATENTS 6/1964 Beese ..313/113 9/1944 Craig ..313/44 X 3/1943 Zodtner ..313/36 X [151 3,684,908 51 Aug. 15, 1972 1,804,349 5/1931 Langmuir ..313/20 2,562,887 8/1951 Beese ..313/25 X 3,497,742 2/1970 Richter ..313/25 X 3,265,885 3/1966 Porter ..240/47 3,402,322 9/1968 Meckler ..313/36 X Primary Examiner-Roy Lake Assistant Examiner-Palmer C. Demeo Attorney-C, Cornell Remsen, Jr., Walter J. Baum, Paul W. Hemminger, Charles L. Johnson, Jr., Philip M. Bolton, Isidore Togut, Edward Goldberg and Menotti J. Lombardi, Jr.

[ ABSTRACT A short arc high intensity xenon lamp is enclosed within a sealed housing made of a light transmissive lens and a parabolic reflector shell. The parabolic shell has a plurality of external air ducts through which air is forced to cool the heated lamp. The air cooled metallic reflector shell permits an increase in efiiciency, light intensity and life of the lamp.

1 1 Claims, 2 Drawing Figures PATENTEDAus 15 m2 q. u w a m E 9 9 0 TC M mufio 4 VA T 8 mm 6 R M V 0 3 N BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to high intensity lamps, and, particularly, to a more efficient arrangement for dissipating heat generated by short are gaseous discharge lamps operating at high temperatures and pressures.

2. Brief Description of the Prior Art As it is known in the art, a short are discharge lamp generally includes an anode and a cathode electrode located within a sealed quartz envelope containing a gas such as xenon, mercury, krypton, etc. and is maintained under high pressure in the order of about atmospheres. The anode and cathode electrodes are aligned axially in the envelope with their tips spaced apart by a predetermined distance to conduct current upon application of high voltage pulses and produce an intense arc emitting a continuous spectrum of useful light. Thus, the short are high intensity lamp has been used as an excellent source of concentrated white light for searchlights, spotlights and the like. In most applications, for good performance, an auxiliary lens has been used to direct the emitted light in a concentrated beam. The light source is generally positioned at the focal point of the accompanying reflecting mirror and the mirror surface is maintained free of dust by enclosing it within a sealed housing.

With ever increasing demand for short are lamps of the afore-described type, their capability as a source of high intensity light has often been stretched beyond the design limits with the resulting detrimental effect of shortening the life of the lamp.

SUMMARY OF THE INVENTION It is therefore the main object of the present invention to provide an improved more efficient high intensity short arc discharge lamp, and, more particularly, to increase the life and light intensity of such a lamp.

In accordance with the present invention, the foregoing object is achieved by providing a novel parabolic reflector shell having a plurality of ducts through which cool air is forced for dissipating heat generated by the lamp. The ducts are disposed to extend radially from a central protruding tubular neck of the reflector shell toward the outer rim to provide passages for the coolant for removing heat from the lamp through the reflector shell.

Preferably, the seams of the fins on the exterior surface of the parabolic shell and the protrusions are formed by hot sprayed aluminum to provide efficient thermal conduction from the interior to the exterior of the shell.

The interior surface of the reflector is coated with a vaporized layer of silver which provides an excellent reflecting surface. Alternatively the interior surface may include a multi-layer interference filter which directs the visible spectra of light toward the light transmissive lens while transmitting infra-red radiant heat of the light therethrough to the exterior of the reflector shell and to the cooling ducts. The improved efficiency of cooling permits a reduction in size of the light source for a given input wattage. In addition, filtering of the air is not necessary since the lamp is in a hermetically sealed unit and the air is external thereto.

These and other objects and features of the present invention may be more fully apprehended from the following description of the embodiments of the novel lamp structure in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a side view in partial cross-section of the high intensity short are lamp and housing therefor with a portion being broken away; and

FIG. 2 is a bottom view of the lamp reflector shell showing the plurality of thermally conductive fins.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the short are lamp envelope is indicated generally at I 1 while the surrounding housing therefore is generally indicated at 12. The envelope ll of the are lamp is constructed to have a centrally enlarged tubular quartz section 13 containing xenon, mercury, krypton, or the like gases sealed therein under a high pressure and end sections 15 and 16. Cathode electrode 17 and anode electrode 18 are of refractory materials, such as tungsten, mounted axially within the end sections 15 and 16 respectively. The electrodes extend into the centrally enlarged envelope section 13, with the tip ends thereof spaced from each other by a short distance for providing a suitable arc.

The housing 12 for the short are lamp 11 includes a pressed glass shell 21 which forms the lens section of the assembly and a thermally conductive parabolic shell 22 which provides the reflector section of the assembly. The inner surface of the parabolic shell is pro vided with a reflective surface coating 23 preferably of vaporized silver having a high polish. The lens 21 and reflector 22 are each formed with neck portions 25 and 26, respectively for mounting the end portions 15 and 16 of the lamp envelope 11. The neck portions 25 and 26 protrude outwardly from the glass shell 21 and the parabolic reflector shell 22 respectively and are positioned diametrically opposite each other. The neck portion 25 acts as a support for the end portion 15 of the lamp which holds the cathode electrode 17 and provides passage for an external lead 29 therethrough to the cathode electrode 17. The anode electrode 18 is held in the quartz end section 16 surrounded by a tubular copper cap member 31. A condluctor lead 32 is connected between the base portion of the anode electrode 18 and the tubular cap 31 to provide electrical continuity from the cap member 31 to the anode electrode 18. A tubular base cap 33 covers the outer end portion 34 of neck 26 of the reflector shell 22 in such a manner that the interior of the housing assembly is sealed off from the atmosphere. The light source is preferably pre-focused before the cap 33 is soldered to shell 22 to insure permanent optical alignment. An electrical lead 36 from an external electrical power source is connected to the tubular copper cap 31 through a passage in the tubular base cap 33.

A ring shaped spacer 38 is positioned between the tubular copper cap 31 and the protruding neck portion of the parabolic reflector shell 22 to hold the anode electrode in position. Preferably the spacer is made of an insulating material having resilient characteristics or of a rigid material having a cooperating spring member to allow for expansion and contraction of the lamp elements when subjected to heat without affecting the seal. In this manner, the spacer prevents the tubular copper cap 31 from creating undue pressure or tension in the parabolic reflector shell while relieving expansion of cap 31 when the lamp is in operation.

As shown in FIG. 2, a plurality of cooling fins 41, 42, 43, 44 and 45 are provided at the exterior surface of the parabolic reflector 22. The fins are preferably made of sheet metal of a highly conductive material such as aluminum or copper. To enhance the thermal conductivity from the parabolic reflector shell to the exterior surface thereof and to the metal cooling fins, the seams between the parabolic reflector and the fins are formed by spraying with hot aluminum.

An outer shell 46 covers the exterior of the parabolic reflector shell 22 and the fins 41-45 in such a manner that a plurality of air passageways or ducts 48, 49, 50, 51 and 52 are formed between the outer shell and the parabolic reflector shell 22. The outer shell 46 is provided with a protruding tubular neck portion 54 substantially concentric with and disposed adjacent the protruding neck portion 26 of the parabolic reflector shell 22. The protruding neck 54 of the outer shell has an opening to admit cooling air into and through the plurality of ducts. The spaces between the reflector shell 22 and the outer shell 46 are dimensioned such that the air flow is maintained as uniform as possible throughout the reflector shell exterior. The protruding fins 41-45 extend radially from the protruding neck portion 54 toward the outer rim 56 of the parabolic reflector 22. Alternatively, the aforedescribed air passage ducts formed by the fins between the outer shell 46 and reflector 22 could also be provided by fins which are integral parts of the same metal shell that forms either the reflector 22 or outer shell 46.

The parabolic reflector shell and the fins are cooled by air flowing through the ducts and a suitable means such as an electric fan, schematically shown as 58, may be used to speed up the passage of air and thus increase the cooling rate.

The light transmissive lens 21 is made of a heavy pressed glass having a ground outer rim l9 hermetically sealed to the outer rim 56 of the parabolic reflector 22 preferably with epoxy cement 59 of a commercially available variety, such as Araldite AN-l 00.

The lamp assembly 11 should be positioned within the housing so that the arc discharge is properly focused and reflected by surface 23 of the reflector 22. This is done by positioning end portions 15 and 16 of the cathode and anode electrodes 17 and 18 with respect to the lens 21 and the reflector 22, and soldering the tubular copper cap member 33 to the protruding neck portion of the parabolic reflector shell 22. The space 61 within the housing assembly between the lens 21 and the reflector 22 around lamp 11 is filled with inert gas such as nitrogen and maintained at a partial atmospheric pressure. Heat is transmitted from the lamp 1 l to the reflector 23 through the gas by radiation and convection currents and through the reflector 23 to the parabolic shell 22 and the fins 4l45 by conduction.

lllustratively, a short arc xenon lamp of 1,000 watts to 1,200 watts power rating can be mounted in a twelve inch diameter silver parabolic reflector in accordance with the present invention. Such a lamp should provide a peak brightness in the order of 10-15 million beam candle power in a narrow beam searchlight or spotlight. In this example, a cooling air flow of 50 to cu. ft. per minute should act as a very effective medium in cooling the parabolic reflector. The high intensity light source of the present invention may find other areas of application besides that of a spotlight and a searchlight, for example, as a modulatable medium for wireless telephone communication in both visible and infrared spectral regions.

It is to be understood that the aforedescribed embodiment is merely illustrative of the application of the principles of the present invention. Numerous other modifications may be made by those ordinarily skilled in the art without departing from the spirit and the scope of the present invention.

What is claimed is:

1. In combination a high intensity lamp and a housing therefore, said housing comprising a light transmissive shell and ametallic reflector shell, said lamp being mounted in a central position between said two shells, the outer rims of said shells being sealed together, said reflector shell having an enclosed central tubular neck and a plurality of external ducts, said ducts including a plurality of thermally conductive fins protruding from the exterior of said reflector shell and extending radially and outwardly from said central neck toward said outer rims, an outer shell engaging and covering said plurality of protruding fins and having a central tubular opening concentric with said tubular neck providing an inlet for a coolant and a peripheral opening around said outer rims providing an outlet for said coolant, said fins providing substantially uniform passages for said coolant extending radially between said reflector and outer shells from said neck to said rims.

2. The combination of a lamp and a housing in accordance with claim 1, wherein each said light transmissive shell and said reflector shell respectively has a tubular neck at the central portion thereof, said high intensity lamp is a short are xenon gas discharge lamp having two end sections mounted within opposite cen tral tubular neck portions and an elongated tubular quartz envelope having a central gaseous discharge section between said end sections, a cathode electrode mounted in the end section within said light transmissive shell and extending into said tubular quartz envelope, an anode electrode mounted in the opposite end section within said reflector shell and extending into said tubular quartz envelope, said electrodes being spaced from each other within said envelope to form an arc discharge gap therebetween, a tubular conductive cap covering the neck portion of said reflector shell and connected to said anode electrode and a cathode connection extending externally through said neck portion of said light transmissive shell.

3. The combination of a lamp and a housing in accordance with claim 2 wherein said reflector and outer shells are of substantially parabolic shape, said arc discharge gap being positioned at the focal point of said parabolic reflector.

4. In combination a high intensity lamp and a housing in accordance with claim 2, including a spacer interposed between the protruding neck portion of said reflector shell and the end section of said tubular quartz envelope, said spacer being resilient to allow thermal contraction and expansion of said quartz envelope and said tubular conductive cap.

5. In combination a high intensity lamp and a housing in accordance with claim 4, including means for directing cooling fluid into and through said plurality of ducts from the protruding neck toward the outer rim.

6. In combination a high intensity lamp and a housing in accordance with claim 5, wherein said reflector shell is of a thermally conductive sheet metal, and said plurality of fins are made of a thermally conductive metal; said fins being jointed to the exterior of said reflector with aluminum seams for increasing thermal heat dissipation.

7. In combination a high intensity lamp and a housing therefor in accordance with claim 6, wherein said fins are integral parts of said reflector shell.

ground outer rim, and an epoxy cement hermetically sealing said outer rim of said glass to the outer rim of said parabolic reflector shell.

9. In combination a high intensity lamp and a housing in accordance with claim 8 wherein the interior surface of said reflector shell includes a layer of vaporized silver deposited thereon for providing a high reflective surface.

10. In combination a high intensity lamp and a housing in accordance with claim 8, including a multi-layer interference filter disposed on the interior surface. of said reflector shell for focusing the visible spectrum of the light being emitted from said lamp toward said light transmissive shell and for transmitting infra-red radiant heat through said reflector shell.

1 1. In combination a high intensity lamp and a housing in accordance with claim 8, wherein the space between said housing and said lamp envelope is filled with an inert gas below atmospheric pressure. 

1. In combination a high intensity lamp and a housing therefore, said housing comprising a light transmissive shell and a metallic reflector shell, said lamp being mounted in a central position between said two shells, the outer rims of said shells being sealed together, said reflector shell having an enclosed central tubular neck and a plurality of external ducts, said ducts including a plurality of thermally conductive fins protruding from the exterior of said reflector shell and extending radially and outwardly from said central neck toward said outer rims, an outer shell engaging and covering said plurality of protruding fins and having a central tubular opening concentric with said tubular neck providing an inlet for a coolant and a peripheral opening around said outer rims providing an outlet for said coolant, said fins providing substantially uniform passages for said coolant extending radially between said reflector and outer shells from said neck to said rims.
 2. The combination of a lamp and a housing in accordance with claim 1, wherein each said light transmissive shell and said reflector shell respectively has a tubular neck at the central portion thereof, said high intensity lamp is a short arc xenon gas discharge lamp having two end sections mounted within opposite central tubular neck portions and an elongated tubular quartz envelope having a central gaseous discharge section between said end sections, a cathode electrode mounted in the end section within said light transmissive shell and extending into said tubular quartz envelope, an anode electrode mounted in the opposite end section within said reflector shell and extending into said tubular quartz envelope, said electrodes being spaced from each other within said envelope to form an arc discharge gap therebetween, a tubular conductive cap covering the neck portion of said reflector shell and connected to said anode electrode and a cathode connection extending externally through said neck portion of said light transmissive shell.
 3. The combination of a lamp and a housing in accordance with claim 2 wherein said reflector and outer shells are of substantially parabolic shape, said arc discharge gap being positioned at the focal point of said parabolic reflector.
 4. In combination a high intensity lamp and a housing in accordance with claim 2, including a spacer interposed between the protruding neck portion of said reflector shell and the end section of said tubular quartz envelope, said spacer being resilient to allow thermal contraction and expansion of said quartz envelope and said tubular conductive cap.
 5. In combination a high intensity lamp and a housing in accordance with claim 4, including means for directing cooling fluid into and through said plurality of ducts from the protruding neck toward the outer rim.
 6. In combination a high intensity lamp and a housing in accordance with claim 5, wherein said reflector shell is of a thermally conductive sheet metal, and said plurality of fins are made of a thermally conductive metal; said fins being jointed to the exterior of said reflector with aluminum seams for increasing thermal heat dissipation.
 7. In combination a high intensity lamp and a housing therefor in accordance with claim 6, wherein said fins are integral parts of said reflector shell.
 8. In combination a high intensity lamp and a housing in accordance with claim 7, wherein said light transmissive shell is a relatively heavy clear glass lens with a ground outer rim, and an epoxy cement hermetically sealing said outer rim of said glass to the outer rim of said parabolic reflector shell.
 9. In combination a high intensity lamp and a housing in accordance with claim 8 wherein the interior surface of said reflector shell includes a layer of vaporized silver deposited thereon for providing a high reflective surface.
 10. In combination a high intensity lamp and a housing in accordance with claIm 8, including a multi-layer interference filter disposed on the interior surface of said reflector shell for focusing the visible spectrum of the light being emitted from said lamp toward said light transmissive shell and for transmitting infra-red radiant heat through said reflector shell.
 11. In combination a high intensity lamp and a housing in accordance with claim 8, wherein the space between said housing and said lamp envelope is filled with an inert gas below atmospheric pressure. 